Lithographic apparatus and scanning method

ABSTRACT

A lithographic apparatus includes a first support to support a first patterning device; a second support to support a second patterning device, each of the first and the second patterning device capable of imparting a radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system to project the patterned radiation beam onto a target portion of the substrate; a controller to drive the first support and the second support and arranged to: drive the first support to perform a scanning movement; drive the second support to accelerate during at least part of the scanning movement of the first support; and drive the second support to perform a scanning movement upon completion of the scanning movement of the first support, so as to scan a die adjacent a die previously scanned during the scanning movement of the first support.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority and benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/310,532, entitled “Lithographic Apparatus and Scanning Method”, filed on Mar. 4, 2010 and U.S. Provisional Patent Application No. 61/331,884, entitled “Lithographic Apparatus and Scanning Method”, filed on May 6, 2010. The contents of these applications are incorporated herein in their entirety by reference.

FIELD

The present invention relates to a lithographic apparatus and a lithographic scanning method.

BACKGROUND

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

In order to make use of a lithographic apparatus as efficiently as possible, it is desirable to achieve a high throughput of the lithographic apparatus, so that a large amount of substrates can be processed by the lithographic apparatus in a shortest possible time.

SUMMARY

It is desirable to provide a lithographic apparatus having a high throughput.

According to an embodiment of the invention, there is provided a lithographic apparatus comprising: a first support constructed to support a first patterning device; a second support constructed to support a second patterning device; wherein the first patterning device is capable of imparting a radiation beam with a pattern in its cross section to form a first patterned radiation beam; wherein the second patterning device is capable of imparting a radiation beam with a pattern in its cross section to form a second patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the first and second patterned radiation beams next to each other onto a target portion of the substrate; a controller configured to drive the first support and the second support, the controller being arranged to: drive the first support to perform a scanning movement; drive the second support to accelerate during at least part of the scanning movement of the first support.

According to an embodiment of the invention, there is provided a lithographic scanning method for projecting patterns from a first patterning device and a second patterning device onto a substrate, the method including performing a scanning movement by a first support configured to hold the first patterning device; accelerating a second support configured to hold the second patterning device, during at least part of the scanning movement of the first support, to a scanning start position and velocity; and performing a scanning movement by the second support upon completion of the scanning movement of the first support, so as to scan a die adjacent a die previously scanned during the scanning movement by the first support.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

FIG. 1 depicts a lithographic apparatus in which an embodiment of the invention may be applied;

FIGS. 2A and 2B each depict a schematic view of a lithographic apparatus in accordance with an embodiment of the invention;

FIGS. 3A and 3B depict a schematic top view of scanning schemes in accordance with an embodiment of the invention; and

FIGS. 4A-4E depict successive support positions of a schematic scanning scheme to illustrate an embodiment of the invention.

FIG. 5 a depicts an intensity of patterned radiation beams onto a wafer.

FIG. 5 b depicts an intensity of patterned radiation beams onto a wafer.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to one embodiment of the invention. The apparatus includes an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation or any other suitable radiation), a patterning device support or support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device in accordance with certain parameters. The apparatus also includes a substrate table (e.g. a wafer table) WT or “substrate support” constructed to hold a substrate (e.g. a resist-coated wafer) W and connected to a second positioning device PW configured to accurately position the substrate in accordance with certain parameters. The apparatus further includes a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. including one or more dies) of the substrate W.

The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, to direct, shape, or control radiation.

The patterning device support holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The patterning device support can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The patterning device support may be a frame or a table, for example, which may be fixed or movable as required. The patterning device support may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section so as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) or more substrate tables or “substrate supports” (and/or two or more mask tables or “mask supports”). In such “multiple stage” machines the additional tables or supports may be used in parallel, or preparatory steps may be carried out on one or more tables or supports while one or more other tables or supports are being used for exposure.

The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, so as to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device (e.g. mask) MA and the projection system. Immersion techniques can be used to increase the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that a liquid is located between the projection system and the substrate during exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD including, for example, suitable directing minors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

The illuminator IL may include an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may include various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

The radiation beam B is incident on the patterning device (e.g., mask MA), which is held on the mask support structure (e.g., mask table MT), and is patterned by the patterning device. Having traversed the patterning device (e.g. mask) MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioning device PW and position sensor IF (e.g. an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioning device PM and another position sensor (which is not explicitly depicted in FIG. 1) can be used to accurately position the patterning device (e.g. mask) MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the patterning device support (e.g. mask table) MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioning device PM. Similarly, movement of the substrate table WT or “substrate support” may be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner) the patterning device support (e.g. mask table) MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device (e.g. mask) MA and substrate W may be aligned using patterning device alignment marks, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device (e.g. mask) MA, the patterning device alignment marks may be located between the dies.

The depicted apparatus could be used in at least one of the following modes:

1. In step mode, the patterning device support (e.g. mask table) MT or “mask support” and the substrate table WT or “substrate support” are kept essentially stationary, while an entire pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT or “substrate support” is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. 2. In scan mode, the patterning device support (e.g. mask table) MT or “mask support” and the substrate table WT or “substrate support” are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT or “substrate support” relative to the patterning device support (e.g. mask table) MT or “mask support” may be determined by the (de-)magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion. 3. In another mode, the patterning device support (e.g. mask table) MT or “mask support” is kept essentially stationary holding a programmable patterning device, and the substrate table WT or “substrate support” is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed and the programmable patterning device is updated as required after each movement of the substrate table WT or “substrate support” or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

Combinations and/or variations on the above described modes of use or entirely different modes of use may also be employed.

As stated above, achieving a high throughput may be considered highly desirable in the lithographic apparatus. In order to be able to achieve such high throughput, many developments have taken place such as for example increasing a scanning speed, optimizing scanning sequences, increasing a effective mask size, making use of dual mask lithography whereby two masks (patterning devices) are projected sequentially onto the substrate, making use of a dual stage configuration whereby leveling measurement and exposure are performed sequentially.

In an embodiment, a gain in throughput may be achieved by equipping the lithographic apparatus with two patterning devices (e.g. mask) stages and two light branches, an example of which is schematically depicted in FIG. 2A: a first light branch that illuminates the first patterning device or reticle (mask) MA of the first patterning or reticle stage MT into a first projection system part PS1, and a second light branch that illuminates the second patterning device or reticle MA2 held by second patterning device or reticle stage MT2 into a second projection system part PS2. Both the first and second light branch couple their image from the first respectively second projection system part PS1, PS2 into a third projection system part PS3 which projects the image onto the substrate W held by substrate table WT. A coupling device CD (e.g. comprising mirrors, switches etc may be provided between the first and second projection system part on the one hand and the third projection system part on the other hand.

As illustrated in FIG. 3A, in a lithographic apparatus according to the state of the art, a scanning movement is performed, by the patterning device or reticle stage MT and the substrate stage WT, whereby the pattern is projected onto a die D1 of the substrate W. Then, both the patterning device or reticle stage and the substrate stage are decelerated, stopped, accelerated in reverse direction and brought to a new scanning position at a desired scanning speed in opposite direction to the previous scan. In between the scans, the substrate table is moved in the X direction. Thereby, a meander shaped pattern of movement is described by the reticle stage and the substrate stage. The total time for exposing a substrate W (such as a wafer) is now formed by a sum of the time periods during which the scanning exposures takes place, and a sum of the time periods during which the stages are brought to a position and speed for each following scan.

In an embodiment of the invention, this time may be reduced considerably as the lithographic apparatus allows to irradiate a pattern onto the substrate via one of the patterning device or reticle stages (e.g. by scanning) while during this scanning time the other patterning device or reticle stage is brought to a starting position and velocity for a following exposure. Thereby, the time required in between exposures may be reduced.

In one embodiment of the invention, two illuminators ILL1, ILL2 (illumination optics) either having a common radiation source, or each being provided with its own radiation source. Switching may be required so as to alternate between the first and second patterning devices or reticles MA, MA2, this switching may be performed in many ways. It is for example possible that two radiation sources are alternately operated. Alternatively, one or more displaceable mirrors or other displaceable optical elements may be provided in an optical path. Depending on a position of the mirror or other optical element, the corresponding beams are directed so as to be projected onto the substrate or not: hence a periodic changing of the position of the mirror or other optical element may result in a desired alternating. Such mirror or other optical element may for example be provided upstream of the third projection system part, so as to allow either light (i.e. a beam) from the first projection system part of from the second projection system part to be projected onto the substrate by the third projection system part. Furthermore, such a mirror or other optical element may be provided upstream of the first and second projection system parts so as to allow or block the corresponding beam to pass through the first and/or second projection system parts (e.g. by blocking or allowing to pass light through the first and second reticle.

FIG. 2B depicts a slightly more detailed schematic view of a part of a lithographic apparatus in accordance with an embodiment of the invention. Here, first and second illuminator optics ILL1 and ILL2 are provided, each comprising a respective reticle mask RMA1, RMA2 and a respective pupil shaper PSR1, PSR2. The illuminator optics provide an optical path through a respective patterning device (e.g. reticle) MA1, MA2 held by a respective support MT1, MT2. The patterning devices and corresponding supports may move along scanning direction SD. The first optical path via the first illuminator and the first patterning device proceeds via projection system part PS1, while the second optical path via the second illuminator and the second patterning device proceeds via projection system part PS2. Respective mirrors MR1 and MR2 reflect both beams, i.e. from the first and second projection system parts, to a mirror structure MR3, which may (as schematically depicted in FIG. 2B) comprise a mirror block or dual mirrors. The beams along the two optical paths then proceed via the third projection system part PS3 so as to be able to project two e.g. adjacent slits (simultaneously and/or subsequently) onto the substrate W.

In an embodiment, there is provided a lithographic apparatus comprising a first support and a second support. The first support is constructed to support a first patterning device. The second support is constructed to support a second patterning device. The first patterning device is capable of imparting a radiation beam with a pattern in its cross section to form a first patterned radiation beam. The second patterning device is capable of imparting a radiation beam with a pattern in its cross section to form a second patterned radiation beam. The lithographic apparatus further comprises a substrate table constructed to hold a substrate, and a projection system. The projection system is configured to project the first and second patterned radiation beams next to each other onto a target portion of the substrate. The lithographic apparatus further comprises a controller configured to drive the first support and the second support and is arranged to drive the first support to perform a scanning movement and drive the second support to accelerate during at least part of the scanning movement of the first support.

The first and second patterned radiation beams may be adjacent to each other or there may be a distance between the two beams. The beams may be projected on the wafer as slits. The beams may be projected onto the same die. Alternatively, each beam may be projected onto a separate die, wherein the dies may be adjacent to each other.

A benefit of projecting the patterned radiation beams next to each other, is that each of the patterned radiation beams may be controlled independently. For example, the light or radiation intensity, also referred to as dose, may be controlled independently. In case both patterned radiation beams are projection simultaneously in the same slit, the dose for each of the beams needs to be controlled to properly project the first and second pattern. Further, the total amount of dose needs to be controlled to achieve a proper illumination of the radiation-sensitive resist on the substrate. It may be difficult to match these 3 parameters. By projecting the patterned radiation beams next to each other, the dose of each beam may be optimized, resulting in a better illumination of the substrate.

When projecting a patterned radiation beam onto the target, the intensity will increase during a short amount of time, before it reaches the desired value, see FIGS. 5 a and 5 b. This is, for example, caused by a shutter member that blocks the patterned beam from entering the projection system. It will take some time to remove the shutter member completely from the beam path, and thus before the full intensity of the beam reaches the target. In the same way, the intensity will decrease a short amount of time before it reaches zero.

FIG. 5 a shows the dose (I) of an embodiment in which both patterned radiation beams are projected in a single slit as function of time (t). Because of the need to control both the dose of each beam, as well as the total amount of dose through the slit, the exposure of the second pattern (P2) starts after the first pattern (P1) has completely finished. During the time, t_(d), between the full dose of P1 and full dose of P2, a pattern may not be projected properly.

FIG. 5 b shows the dose (I) of an embodiment in which each patterned radiation beam is projected through a separate slit. When the first pattern P1 is still being exposed at full dose, the exposure of the second pattern P2 may be started. This way, the second pattern P2 is at full dose when the first pattern P1 starts to decrease. This allows the patterns to be projected more fastly after each other. This may allow to projected adjacent dies more closely next to each other. Alternatively, the two patterns may be patterned at the same time.

Alternatively, in the configuration in FIG. 2B, the mirror structure MR3 may be replaced by a combiner, such as a polygon or any other combiner, which may enable to project the beams of both optical paths into a same slit. In the embodiment in accordance with FIG. 2B, the dual slits may be in use (i.e. projecting a respective beam) simultaneously, e.g. at a takeover where a scan of the first patterning device or reticle MA1 ends, while a scan of the other patterning device or reticle MA2 begins, so as to allow an efficient and fast takeover. In that case it may be desirable to make use of two radiation sources in order to allow the projection of the beams along the two optical paths simultaneously. A single radiation source may be applied, however in that case the two patterning device or masks may only be illuminated without overlap in time. In the alternative as described above, wherein a combiner is used, a single radiation source may be applied instead of the dual sources.

The different optical paths may each have a different transmission characteristic and a different degradation over time. Furthermore, the different radiation sources may result in differences in optical dose. It may be desirable to control a dose so that via the different paths and/or from the different radiation sources, a similar dose is obtained at a substrate level. An embodiment of a control strategy to achieve this goal is provided by measuring a non-overlapping part of each of the optical paths and adjusting a dose of the radiation source respectively the radiation sources so as to compensate for the measured difference in transmission characteristics of the non overlapping parts of the optical paths. In the case of a single, common radiation source, the dose of the source which alternately transmits via the first and second optical paths, is adjusted alternately to the transmission characteristics of the optical path that is applied at that moment. In case of two radiation sources, the dose of each of the radiation sources is adjusted in accordance with the transmission characteristics of the path via which the respective radiation source is to transmit.

Each projection element may be prone to tolerances which may result in an error of the projection by the projection system. Optimizing a projection, one or more controllable optical elements may be applied, such as a mirror or lens of which a position is controlled and driven by an actuator, such as a so called lens manipulator. In the projection system having two optical paths, different errors may occur in each path. In the projection system in accordance with an embodiment of the invention, in an embodiment, the error(s) may at least partly be corrected by an adjustable optical element in each of the paths (e.g. in projection system parts PS1, PS2). Thereby, the common part of the paths (e.g. the third projection system part PS3) may be held uncorrected, provided a sufficiently large range of correction is provided in both paths (e.g. in projection system parts PS1, PS2). In another embodiment, correction may be provided in each of the projection system parts PS1, PS2 and PS3. Hence, the correction in PS1 and PS3 together allow correction of the first path, while the correction in PS2 and PS3 together allow correction of the second path.

Substrate leveling measurement may be configured to cope with a higher throughput. Thereto, many approaches may be followed. Some examples will now be described for a dual stage lithographic apparatus, i.e. a lithographic apparatus wherein exposure is performed at an exposure side, while at the same time a leveling measurement is performed on another substrate. Given the shorter exposure cycle that may be achieved in accordance with an embodiment of the invention, providing an improved leveling measurement may be desirable. In an embodiment, dual leveling sensors may be provided, the lithographic apparatus being configured to measure in parallel with the two leveling sensors, so that the surface on which the leveling measurement is to be performed, may be measured in a shorter time period. Alternatively, dual leveling sensors may be configured as a coarse leveling sensor and a fine leveling sensor. Thereby, a higher measurement speed may be achieved, which may have a favorable effect on total time required to perform a leveling measurement. Leveling measurement may also be performed in a handler. In an embodiment, a coarse leveling may be performed in the handler, while the fine leveling measurement is performed at the measure side of the lithographic apparatus. In another embodiment of the invention, part of the leveling (e.g. coarse leveling measurement) is performed at the measure side of the lithographic apparatus, while part of the leveling (e.g. the fine leveling measurement) is performed by a corresponding level sensor at the expose side.

It will be appreciated that FIGS. 2A and 2B are to be considered as schematic configurations intended to illustrate the concepts described in this document. In a practical embodiment, there may for example be a larger spacing between the first and second supports, so as to allow them to move independently.

The lithographic apparatus is accordance with an embodiment of the invention may be applied for a variety of scanning schemes. As referred to above and described with reference to FIG. 3A, in a conventional lithographic apparatus, a meander shaped scanning pattern is usually applied, whereby the patterning device or reticle stage MT and the substrate table WT each perform a scanning movement in order to repetitively expose the pattern onto the substrate. In accordance with an embodiment of the invention, adjacent dies in a row or column are successively scanned. Thereto, a first die D1 is scanned by the first patterning device or reticle, a second, following die D2 by the second patterning device or reticle, a third die D3 again by the first patterning device or reticle, a fourth die D4 by the second patterning device or reticle, and etc. This scanning is further explained with reference to FIGS. 4A-4E. FIGS. 4A-4E each show a schematic view of successive steps of a reticle scanning movement. In each of these Figures, the first patterning device or reticle stage MT is depicted at the left side, and the second reticle or patterning device stage MT2 at the right side. An arrow in each of the patterning devices or reticles indicates a direction in which the reticle moves. In the examples, it is assumed that the scanning direction is the y direction. Where no arrow is depicted in the patterning device or reticle, it has stopped. In FIG. 4A, the first patterning device or reticle is at scanning speed and starts to perform a scan. At that moment in time, the second patterning device or reticle has just completed a scan (as symbolically indicated by the passing of the dotted lines). Then, in FIG. 4B, the second patterning device or reticle has decelerated and stopped, while the first reticle performs the scan. During the scan of the first patterning device or reticle, the second patterning device or reticle accelerates and moves in reverse direction (FIG. 4C), decelerates and stops (FIG. 4D), and accelerates again in scanning direction to scanning speed (FIG. 4E). At that moment, the scanning by the first patterning device or reticle is substantially completed, and the light paths are changed so as to project the pattern of the second reticle on the substrate instead of the pattern of the first patterning device or reticle. Now, the pattern of the second patterning device or reticle is scanned. The substrate may move at a constant velocity during the scanning. The process as described here may result in the successive projections of adjacent dies as depicted in FIG. 3B. The controller which drives the first and second support (i.e. first and second patterning device or reticle stages) may be arranged to activate a first optical path via the first projection system part PS1 during the scanning movement of the patterning device or reticle stage MT and to activate a second optical path via the second projection system part PS2 during the scanning movement of the second support MT2.

With the method according to an embodiment of the invention, the same or similar benefits may be achieved as with the lithographic apparatus. With the method according to an embodiment of the invention, the same or similar preferred embodiments may be provided, thereby achieving the same or similar effects as corresponding preferred embodiments of the lithographic apparatus.

In an embodiment of the invention, the lithographic apparatus may also be described as: a lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; and a projection system configured to project the patterned radiation beam onto a target portion of the substrate, wherein the lithographic apparatus further comprises a second support constructed to support a second patterning device; and a controller to drive the support and the second support, the controller being arranged to: drive the support to perform a scanning movement; drive the second support to accelerate, during at least part of the scanning movement of the support, to a scanning start position and velocity; and drive the second support to perform a scanning movement upon completion of the scanning movement of the support, so as to scan an adjacent die. It will be understood that the same embodiments, features, effects etc as described in this document, also apply to the lithographic apparatus as described here.

Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion”, respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the invention may take the form of a computer program containing one or more sequences of machine-readable instructions describing a method as disclosed above, or a data storage medium (e.g. semiconductor memory, magnetic or optical disk) having such a computer program stored therein.

The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below. 

1. A lithographic apparatus comprising: a first support constructed to support a first patterning device; a second support constructed to support a second patterning device; wherein the first patterning device is capable of imparting a radiation beam with a pattern in its cross section to form a first patterned radiation beam; wherein the second patterning device is capable of imparting a radiation beam with a pattern in its cross section to form a second patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the first and second patterned radiation beams next to each other onto a target portion of the substrate; and a controller configured to drive the first support and the second support, the controller being arranged to: drive the first support to perform a scanning movement; drive the second support to accelerate during at least part of the scanning movement of the first support.
 2. The lithographic apparatus of claim 1, wherein the projection system is configured to project the first and second patterned radiation beams adjacent to each other.
 3. The lithographic apparatus of claim 1, wherein the controller is further arranged to drive the second support to perform a scanning movement upon completion of the scanning movement of the first support, so as to scan a die adjacent a die previously scanned during the scanning movement of the first support.
 4. The lithographic apparatus of claim 3, wherein the controller is further arranged to drive the substrate table at a substantially constant substrate table scanning velocity during the scanning movement of the first support and the scanning movement of the second support.
 5. The lithographic apparatus of claim 1, wherein the projection system is arranged to alternately project the pattern of the patterning device and the second patterning device onto a row or column of adjacent dies.
 6. The lithographic apparatus of claims 1, wherein the second support is moved, during the scanning movement of the support, to a scanning start position and velocity by: decelerating the second support from a previous scanning movement; stopping the second support; accelerating the second support to move back in a direction reverse to the scanning movement; decelerating and stopping the second support; and accelerating the second support to the scanning speed.
 7. The lithographic apparatus of claim 1, wherein the second support is moved during the scanning movement of the first support, to a scanning start position and velocity by: decelerating the second support from a previous scanning movement; stopping the second support; and accelerating the second support to the scanning speed in reverse direction as compared to the previous scanning movement of the second support.
 8. The lithographic apparatus of claim 1, wherein the projection system comprises: a first projection system part configured to project a beam patterned by the first patterning device held by the first support; a second projection system part configured to project a beam patterned by the second patterning device held by the second support; and a third projection system part configured to project the patterned beam projected by the first and/or second projection system parts onto the substrate.
 9. The lithographic apparatus of claim 7, wherein the controller is arranged to activate a first optical path via the first projection system part during the scanning movement of the first support and to activate a second optical path via the second projection system part during the scanning movement of the second support.
 10. The lithographic apparatus of claim 1, comprising an illumination system comprising a first illuminator configured to illuminate the patterning device held by the first support and a second illuminator configured to illuminate the second patterning device held by the second support.
 11. The lithographic apparatus of claim 10, wherein the illumination system comprises two sources of radiation
 12. The lithographic apparatus of claim 1, comprising an optical switch arranged to couple the patterned beam into a first projection system part and/or a second projection system part of the projection system.
 13. The lithographic apparatus of claim 1, wherein the lithographic apparatus is a dual stage lithographic apparatus comprising a measurement part configured to perform a substrate levelling measurement, and an exposure part, the lithographic apparatus comprising dual levelling sensors at the measurement part.
 14. The lithographic apparatus of claim 13, wherein the dual levelling sensors comprise a coarse levelling sensor and a fine levelling sensor.
 15. The lithographic apparatus of claim 14, wherein the dual levelling sensors are configured to each measure in parallel a part of a surface of the substrate.
 16. The lithographic apparatus of claim 1, wherein the lithographic apparatus is a dual stage lithographic apparatus comprising a measurement part configured to perform a substrate levelling measurement, and an exposure part, the lithographic apparatus comprising a levelling sensor at the measure part and a levelling sensor at the exposure part.
 17. The lithographic apparatus of claim 1, wherein, in use, the second support accelerates during the at least part of the scanning movement of the first support to a scanning start position and velocity.
 18. A combination of a lithographic apparatus of claim 1 and a handler, the hander comprising a leveling sensor configured to perform a substrate leveling measurement.
 19. A lithographic scanning method for projecting patterns from a first patterning device and a second patterning device onto a substrate, the method comprising: performing a scanning movement by a first support configured to hold the first patterning device; accelerating a second support configured to hold the second patterning device, during at least part of the scanning movement of the first support, to a scanning start position and velocity; and performing a scanning movement by the second support upon completion of the scanning movement of the first support, so as to scan a die adjacent a die previously scanned during the scanning movement by the first support.
 20. The method of claim 19, wherein, in use, the second support accelerates during the at least part of the scanning movement of the first support to a scanning start position and velocity. 